(1) Field of the Invention
The present invention relates to a technology which improves fluidity of a liquid crystalline polyester composition, and a technology which improves warp resistance and crack resistance of a connector formed by using the same.
(2) Description of Related Art
As a connector for electronic components, for example, a CPU socket is known. The CPU socket is a connector for detachably mounting a central processing unit (CPU) to an electronic circuit board. The CPU socket can be, for example, formed of a resin having excellent heat resistance.
As an electronic equipment with high performance has been developed, the scale of a circuit of CPU to be mounted on an electronic circuit board has increased. Generally, as the scale of CPU increases, the number of contact pins increases. Recently, CPU including about 700 to 1,000 contact pins has been known. The contact pins of CPU are disposed on a bottom face of CPU, for example, in a matrix form. A pitch of these contact pins tends to decrease as the number of the contact pins increases. Also, as the scale of IC increases, a calorific value tends to increase.
The CPU socket includes pin insertion holes corresponding to each contact pin of CPU. As the pitch of the contact pins decreases, the pitch of the pin insertion holes decreases and therefore, a width of a resin which partitions the pin insertion holes each other decreases. Therefore, in the CPU socket, as the number of the pin insertion holes increases, warp and crack are likely to be caused by reflow soldering or pin insertion.
Also, the CPU socket is generally produced by using an injection molding method. However, when the portion where the pin insertion holes are partitioned each other has a small width, partial poor filling (i.e., a phenomenon of lack of a filling amount of a resin) is likely to arise when a mold is filled with a resin. At the portion where poor filling occurred, a mechanical strength becomes insufficient. In order to suppress the occurrence of poor filling, it is necessary to sufficiently enhance fluidity of a resin composition.
A technology of suppressing warp and crack of the CPU socket or the other connector for electronic components is disclosed, for example, in JP-A-2005-276758, JP-A-8-325446, JP-A-2001-106923 and JP-A-2006-274068.
JP-A-2005-276758 discloses a CPU socket formed of a composition obtained by mixing a fibrous filler in a liquid crystalline polymer (see paragraph [0017] of JP-A-2005-276758). According to the technology of JP-A-2005-276758, an attempt is made to suppress warp of the CPU socket and to improve fluidity by using such a composition (see paragraph [0008] of JP-A-2005-276758).
JP-A-8-325446 discloses a connector formed of a composition obtained by filling a liquid crystalline polyester resin with glass beads (see paragraph [0006] of JP-A-8-325446). According to the technology of JP-A-8-325446, an attempt is made to improve a mechanical strength of the connector by using such a composition (see paragraph [0038] of JP-A-8-325446).
JP-A-2001-106923 discloses a connector formed of a composition obtained by mixing a plate-like filler with a liquid crystalline polymer or a composition obtained by mixing a plate-like filler and a fibrous filler with a liquid crystalline polymer (see paragraphs [0013] and [0018] of JP-A-2001-106923). According to the technology of JP-A-2001-106923, an attempt is made to suppress warp of the connector by mixing a plate-like filler and to improve a mechanical strength of the connector by mixing a fibrous filler (see paragraph [0013] and [0018] of JP-A-2001-106923).
JP-A-2006-274068 discloses a connector formed of a composition obtained by mixing a scaly reinforcer with a liquid crystalline resin or a composition obtained by mixing a scaly reinforcer and a fibrous reinforcer with a liquid crystalline resin (see paragraphs [0006] and [0008] of JP-A-2006-274068). According to the technology of JP-A-2006-274068, an attempt is made to suppress blister upon reflow soldering (see paragraph [0011] of JP-A-2006-274068).
However, when a CPU socket includes quite a lot of pin insertion holes (therefore, when a resin which partitions pin insertion holes is very fine), it was impossible to sufficiently suppress warp, crack and poor filling even in the case of using the above technologies of JP-A-2005-276758, JP-A-8-325446, JP-A-2001-106923 and JP-A-2006-274068.
On the other hand, when a liquid crystalline polymer was allowed to contain only a fibrous filler, a liquid composition did not have sufficient fluidity, and poor filling was likely to occur.
Also, when a liquid crystalline polymer was allowed to contain only a plate-like filler, although poor filling was less likely to occur, shrinkage was likely to occur, and thus warp and crack were likely to occur.
Furthermore, when a liquid crystalline polymer was allowed to contain both a fibrous filler and a plate-like filler, although the occurrence of poor filling and warp is suppressed, crack was likely to occur.